Ultrahigh voltage transmission lines play a key role in power transmission across the country, and inspection/management of transmission lines is a critical task in effectively ensuring the safety of power transmission and distribution lines as well as the related equipment. Currently, inspection of power lines in many countries including China still relies on manual record, which has the disadvantages of being costly and risky with possible inspection missing. Over the past two decades, aerial inspection was used for inspection of Ultrahigh voltage transmission lines, which significantly improved the efficiency and precision of detection. However, such a method is restricted by flight safety, airline control, weather conditions and refueling requirements. To ensure flight safety, it requires not only many security measures but also extensive training of pilots on operation and inspection skills. As a result, helicopter inspection met difficulty in gaining popularity. Recently, unmanned aerial vehicle (UAV) was also used to inspect power lines. However, the safety issues and short of endurance hamper its further application.
Rapid development of space technology helped to improve the ability to obtain spatial surface information. Many commercial satellites had achieved spatial resolutions in the range of sub-meter and the revisit cycle had also shortened to one day. Currently, the most commonly used commercial satellites with high resolution include QuickBird, GeoEye-1 and Worldview, and the highest achievable resolution is 0.41 meter. It is expected that higher resolution will be available in the future, which makes it possible to inspect power lines by using the satellite sensing technologies.
Except for research on identifying and extracting power lines from images taken aerially and LiDAR data, currently there is hardly any other research on power line identification and extraction by using satellite remote sensing images across the world, which is due to the characteristics of having sub-pixels, weak objects and complicated background of satellite remote sensing images. However, high resolution satellite remote sensing images have irreplaceable advantages in terms of cycle, cost and efficiency of acquisition. Therefore, an urgent problem to be solved is to identify and extract a weak linear object such as a power line from images having sub-pixels, weak objects and complicated background, such as satellite images.